// let config = {
//   SIM_RESOLUTION: 128,
//   DYE_RESOLUTION: 1024,
//   CAPTURE_RESOLUTION: 512,
//   DENSITY_DISSIPATION: 1,
//   VELOCITY_DISSIPATION: 0.2,
//   PRESSURE: 0.8,
//   PRESSURE_ITERATIONS: 20,
//   CURL: 30,
//   SPLAT_RADIUS: 0.25,
//   SPLAT_FORCE: 6000,
//   SHADING: true,
//   COLORFUL: true,
//   COLOR_UPDATE_SPEED: 10,
//   PAUSED: false,
//   BACK_COLOR: { r: 255, g: 255, b: 255 },
//   TRANSPARENT: false,
//   BLOOM: true,
//   BLOOM_ITERATIONS: 8,
//   BLOOM_RESOLUTION: 256,
//   BLOOM_INTENSITY: 0.8,
//   BLOOM_THRESHOLD: 0.6,
//   BLOOM_SOFT_KNEE: 0.7,
//   SUNRAYS: true,
//   SUNRAYS_RESOLUTION: 196,
//   SUNRAYS_WEIGHT: 1.0,
// };

// mouseMoveRender：是否开启鼠标移动渲染（无需按下鼠标）
export function webglFluidSimulationStart(canvasEle, initConfig) {
  const canvas = canvasEle;

  const glContext = getWebGLContext(canvas);
  if (!glContext) return null;
  const { gl, ext } = glContext;

  let config = Object.assign(
    {
      SIM_RESOLUTION: 128,
      DYE_RESOLUTION: 1024,
      CAPTURE_RESOLUTION: 512,
      DENSITY_DISSIPATION: 1,
      VELOCITY_DISSIPATION: 0.2,
      PRESSURE: 0.8,
      PRESSURE_ITERATIONS: 20,
      CURL: 30,
      SPLAT_RADIUS: 1,
      SPLAT_FORCE: 6000,
      SHADING: true, // 是否开启着色
      COLORFUL: true,
      COLOR_UPDATE_SPEED: 10,
      PAUSED: false,
      BACK_COLOR: { r: 255, g: 255, b: 255 },
      TRANSPARENT: false,
      BLOOM: false,
      BLOOM_ITERATIONS: 8,
      BLOOM_RESOLUTION: 256,
      BLOOM_INTENSITY: 0.8,
      BLOOM_THRESHOLD: 0.6,
      BLOOM_SOFT_KNEE: 0.7,
      SUNRAYS: false,
      SUNRAYS_RESOLUTION: 196,
      SUNRAYS_WEIGHT: 1.0,
      // 扩展配置
      TRIGGER: 'click',
    },
    initConfig
  );

  let animationFrameId;
  const eventListeners = {
    mouseDown: null,
    mouseMove: null,
    mouseUp: null,
    touchStart: null,
    touchMove: null,
    touchEnd: null,
    keyDown: null,
  };

  let pointers = [];
  let splatStack = [];
  pointers.push(new pointerPrototype());

  function pointerPrototype() {
    this.id = -1;
    this.texcoordX = 0;
    this.texcoordY = 0;
    this.prevTexcoordX = 0;
    this.prevTexcoordY = 0;
    this.deltaX = 0;
    this.deltaY = 0;
    this.down = false;
    this.moved = false;
    this.color = [30, 0, 300];
  }

  if (isMobile()) {
    config.DYE_RESOLUTION = 512;
  }
  if (!ext.supportLinearFiltering) {
    config.DYE_RESOLUTION = 512;
    config.SHADING = false;
    config.BLOOM = false;
    config.SUNRAYS = false;
  }

  function getWebGLContext(canvas) {
    try {
      const params = {
        alpha: true,
        depth: false,
        stencil: false,
        antialias: false,
        preserveDrawingBuffer: false,
      };

      let gl = canvas.getContext('webgl2', params);
      const isWebGL2 = !!gl;
      if (!isWebGL2)
        gl =
          canvas.getContext('webgl', params) ||
          canvas.getContext('experimental-webgl', params);

      let halfFloat;
      let supportLinearFiltering;
      if (isWebGL2) {
        gl.getExtension('EXT_color_buffer_float');
        supportLinearFiltering = gl.getExtension('OES_texture_float_linear');
      } else {
        halfFloat = gl.getExtension('OES_texture_half_float');
        supportLinearFiltering = gl.getExtension(
          'OES_texture_half_float_linear'
        );
      }

      gl.clearColor(0.0, 0.0, 0.0, 1.0);

      const halfFloatTexType = isWebGL2
        ? gl.HALF_FLOAT
        : halfFloat.HALF_FLOAT_OES;
      let formatRGBA;
      let formatRG;
      let formatR;

      if (isWebGL2) {
        formatRGBA = getSupportedFormat(
          gl,
          gl.RGBA16F,
          gl.RGBA,
          halfFloatTexType
        );
        formatRG = getSupportedFormat(gl, gl.RG16F, gl.RG, halfFloatTexType);
        formatR = getSupportedFormat(gl, gl.R16F, gl.RED, halfFloatTexType);
      } else {
        formatRGBA = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        formatRG = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        formatR = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
      }

      return {
        gl,
        ext: {
          formatRGBA,
          formatRG,
          formatR,
          halfFloatTexType,
          supportLinearFiltering,
        },
      };
    } catch (error) {
      console.error('WebGL 初始化失败:', e);
      return null;
    }
  }

  function getSupportedFormat(gl, internalFormat, format, type) {
    if (!supportRenderTextureFormat(gl, internalFormat, format, type)) {
      switch (internalFormat) {
        case gl.R16F:
          return getSupportedFormat(gl, gl.RG16F, gl.RG, type);
        case gl.RG16F:
          return getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, type);
        default:
          return null;
      }
    }

    return {
      internalFormat,
      format,
    };
  }

  function supportRenderTextureFormat(gl, internalFormat, format, type) {
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(
      gl.TEXTURE_2D,
      0,
      internalFormat,
      4,
      4,
      0,
      format,
      type,
      null
    );

    let fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(
      gl.FRAMEBUFFER,
      gl.COLOR_ATTACHMENT0,
      gl.TEXTURE_2D,
      texture,
      0
    );

    let status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
    return status == gl.FRAMEBUFFER_COMPLETE;
  }

  function isMobile() {
    return /Mobi|Android/i.test(navigator.userAgent);
  }

  class Material {
    constructor(vertexShader, fragmentShaderSource) {
      this.vertexShader = vertexShader;
      this.fragmentShaderSource = fragmentShaderSource;
      this.programs = [];
      this.activeProgram = null;
      this.uniforms = [];
    }

    setKeywords(keywords) {
      let hash = 0;
      for (let i = 0; i < keywords.length; i++) hash += hashCode(keywords[i]);

      let program = this.programs[hash];
      if (program == null) {
        let fragmentShader = compileShader(
          gl.FRAGMENT_SHADER,
          this.fragmentShaderSource,
          keywords
        );
        program = createProgram(this.vertexShader, fragmentShader);
        this.programs[hash] = program;
      }

      if (program == this.activeProgram) return;

      this.uniforms = getUniforms(program);
      this.activeProgram = program;
    }

    bind() {
      gl.useProgram(this.activeProgram);
    }
  }

  class Program {
    constructor(vertexShader, fragmentShader) {
      this.uniforms = {};
      this.program = createProgram(vertexShader, fragmentShader);
      this.uniforms = getUniforms(this.program);
    }

    bind() {
      gl.useProgram(this.program);
    }
  }

  function createProgram(vertexShader, fragmentShader) {
    let program = gl.createProgram();
    gl.attachShader(program, vertexShader);
    gl.attachShader(program, fragmentShader);
    gl.linkProgram(program);

    if (!gl.getProgramParameter(program, gl.LINK_STATUS))
      console.trace(gl.getProgramInfoLog(program));

    return program;
  }

  function getUniforms(program) {
    let uniforms = [];
    let uniformCount = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
    for (let i = 0; i < uniformCount; i++) {
      let uniformName = gl.getActiveUniform(program, i).name;
      uniforms[uniformName] = gl.getUniformLocation(program, uniformName);
    }
    return uniforms;
  }

  function compileShader(type, source, keywords) {
    source = addKeywords(source, keywords);

    const shader = gl.createShader(type);
    gl.shaderSource(shader, source);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
      console.trace(gl.getShaderInfoLog(shader));

    return shader;
  }

  function addKeywords(source, keywords) {
    if (keywords == null) return source;
    let keywordsString = '';
    keywords.forEach((keyword) => {
      keywordsString += '#define ' + keyword + '\n';
    });
    return keywordsString + source;
  }

  const baseVertexShader = compileShader(
    gl.VERTEX_SHADER,
    `
    precision highp float;

    attribute vec2 aPosition;
    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform vec2 texelSize;

    void main () {
        vUv = aPosition * 0.5 + 0.5;
        vL = vUv - vec2(texelSize.x, 0.0);
        vR = vUv + vec2(texelSize.x, 0.0);
        vT = vUv + vec2(0.0, texelSize.y);
        vB = vUv - vec2(0.0, texelSize.y);
        gl_Position = vec4(aPosition, 0.0, 1.0);
    }
`
  );

  const blurVertexShader = compileShader(
    gl.VERTEX_SHADER,
    `
    precision highp float;

    attribute vec2 aPosition;
    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    uniform vec2 texelSize;

    void main () {
        vUv = aPosition * 0.5 + 0.5;
        float offset = 1.33333333;
        vL = vUv - texelSize * offset;
        vR = vUv + texelSize * offset;
        gl_Position = vec4(aPosition, 0.0, 1.0);
    }
`
  );

  const blurShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    uniform sampler2D uTexture;

    void main () {
        vec4 sum = texture2D(uTexture, vUv) * 0.29411764;
        sum += texture2D(uTexture, vL) * 0.35294117;
        sum += texture2D(uTexture, vR) * 0.35294117;
        gl_FragColor = sum;
    }
`
  );

  const copyShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying highp vec2 vUv;
    uniform sampler2D uTexture;

    void main () {
        gl_FragColor = texture2D(uTexture, vUv);
    }
`
  );

  const clearShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying highp vec2 vUv;
    uniform sampler2D uTexture;
    uniform float value;

    void main () {
        gl_FragColor = value * texture2D(uTexture, vUv);
    }
`
  );

  const colorShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;

    uniform vec4 color;

    void main () {
        gl_FragColor = color;
    }
`
  );

  const checkerboardShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    uniform sampler2D uTexture;
    uniform float aspectRatio;

    #define SCALE 25.0

    void main () {
        vec2 uv = floor(vUv * SCALE * vec2(aspectRatio, 1.0));
        float v = mod(uv.x + uv.y, 2.0);
        v = v * 0.1 + 0.8;
        gl_FragColor = vec4(vec3(v), 1.0);
    }
`
  );

  const displayShaderSource = `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uTexture;
    uniform sampler2D uBloom;
    uniform sampler2D uSunrays;
    uniform sampler2D uDithering;
    uniform vec2 ditherScale;
    uniform vec2 texelSize;

    vec3 linearToGamma (vec3 color) {
        color = max(color, vec3(0));
        return max(1.055 * pow(color, vec3(0.416666667)) - 0.055, vec3(0));
    }

    void main () {
        vec3 c = texture2D(uTexture, vUv).rgb;

    #ifdef SHADING
        vec3 lc = texture2D(uTexture, vL).rgb;
        vec3 rc = texture2D(uTexture, vR).rgb;
        vec3 tc = texture2D(uTexture, vT).rgb;
        vec3 bc = texture2D(uTexture, vB).rgb;

        float dx = length(rc) - length(lc);
        float dy = length(tc) - length(bc);

        vec3 n = normalize(vec3(dx, dy, length(texelSize)));
        vec3 l = vec3(0.0, 0.0, 1.0);

        float diffuse = clamp(dot(n, l) + 0.7, 0.7, 1.0);
        c *= diffuse;
    #endif

    #ifdef BLOOM
        vec3 bloom = texture2D(uBloom, vUv).rgb;
    #endif

    #ifdef SUNRAYS
        float sunrays = texture2D(uSunrays, vUv).r;
        c *= sunrays;
    #ifdef BLOOM
        bloom *= sunrays;
    #endif
    #endif

    #ifdef BLOOM
        float noise = texture2D(uDithering, vUv * ditherScale).r;
        noise = noise * 2.0 - 1.0;
        bloom += noise / 255.0;
        bloom = linearToGamma(bloom);
        c += bloom;
    #endif

        float a = max(c.r, max(c.g, c.b));
        gl_FragColor = vec4(c, a);
    }
`;

  const bloomPrefilterShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying vec2 vUv;
    uniform sampler2D uTexture;
    uniform vec3 curve;
    uniform float threshold;

    void main () {
        vec3 c = texture2D(uTexture, vUv).rgb;
        float br = max(c.r, max(c.g, c.b));
        float rq = clamp(br - curve.x, 0.0, curve.y);
        rq = curve.z * rq * rq;
        c *= max(rq, br - threshold) / max(br, 0.0001);
        gl_FragColor = vec4(c, 0.0);
    }
`
  );

  const bloomBlurShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uTexture;

    void main () {
        vec4 sum = vec4(0.0);
        sum += texture2D(uTexture, vL);
        sum += texture2D(uTexture, vR);
        sum += texture2D(uTexture, vT);
        sum += texture2D(uTexture, vB);
        sum *= 0.25;
        gl_FragColor = sum;
    }
`
  );

  const bloomFinalShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uTexture;
    uniform float intensity;

    void main () {
        vec4 sum = vec4(0.0);
        sum += texture2D(uTexture, vL);
        sum += texture2D(uTexture, vR);
        sum += texture2D(uTexture, vT);
        sum += texture2D(uTexture, vB);
        sum *= 0.25;
        gl_FragColor = sum * intensity;
    }
`
  );

  const sunraysMaskShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    uniform sampler2D uTexture;

    void main () {
        vec4 c = texture2D(uTexture, vUv);
        float br = max(c.r, max(c.g, c.b));
        c.a = 1.0 - min(max(br * 20.0, 0.0), 0.8);
        gl_FragColor = c;
    }
`
  );

  const sunraysShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    uniform sampler2D uTexture;
    uniform float weight;

    #define ITERATIONS 16

    void main () {
        float Density = 0.3;
        float Decay = 0.95;
        float Exposure = 0.7;

        vec2 coord = vUv;
        vec2 dir = vUv - 0.5;

        dir *= 1.0 / float(ITERATIONS) * Density;
        float illuminationDecay = 1.0;

        float color = texture2D(uTexture, vUv).a;

        for (int i = 0; i < ITERATIONS; i++)
        {
            coord -= dir;
            float col = texture2D(uTexture, coord).a;
            color += col * illuminationDecay * weight;
            illuminationDecay *= Decay;
        }

        gl_FragColor = vec4(color * Exposure, 0.0, 0.0, 1.0);
    }
`
  );

  const splatShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    uniform sampler2D uTarget;
    uniform float aspectRatio;
    uniform vec3 color;
    uniform vec2 point;
    uniform float radius;

    void main () {
        vec2 p = vUv - point.xy;
        p.x *= aspectRatio;
        vec3 splat = exp(-dot(p, p) / radius) * color;
        vec3 base = texture2D(uTarget, vUv).xyz;
        gl_FragColor = vec4(base + splat, 1.0);
    }
`
  );

  const advectionShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    uniform sampler2D uVelocity;
    uniform sampler2D uSource;
    uniform vec2 texelSize;
    uniform vec2 dyeTexelSize;
    uniform float dt;
    uniform float dissipation;

    vec4 bilerp (sampler2D sam, vec2 uv, vec2 tsize) {
        vec2 st = uv / tsize - 0.5;

        vec2 iuv = floor(st);
        vec2 fuv = fract(st);

        vec4 a = texture2D(sam, (iuv + vec2(0.5, 0.5)) * tsize);
        vec4 b = texture2D(sam, (iuv + vec2(1.5, 0.5)) * tsize);
        vec4 c = texture2D(sam, (iuv + vec2(0.5, 1.5)) * tsize);
        vec4 d = texture2D(sam, (iuv + vec2(1.5, 1.5)) * tsize);

        return mix(mix(a, b, fuv.x), mix(c, d, fuv.x), fuv.y);
    }

    void main () {
    #ifdef MANUAL_FILTERING
        vec2 coord = vUv - dt * bilerp(uVelocity, vUv, texelSize).xy * texelSize;
        vec4 result = bilerp(uSource, coord, dyeTexelSize);
    #else
        vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;
        vec4 result = texture2D(uSource, coord);
    #endif
        float decay = 1.0 + dissipation * dt;
        gl_FragColor = result / decay;
    }`,
    ext.supportLinearFiltering ? null : ['MANUAL_FILTERING']
  );

  const divergenceShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uVelocity;

    void main () {
        float L = texture2D(uVelocity, vL).x;
        float R = texture2D(uVelocity, vR).x;
        float T = texture2D(uVelocity, vT).y;
        float B = texture2D(uVelocity, vB).y;

        vec2 C = texture2D(uVelocity, vUv).xy;
        if (vL.x < 0.0) { L = -C.x; }
        if (vR.x > 1.0) { R = -C.x; }
        if (vT.y > 1.0) { T = -C.y; }
        if (vB.y < 0.0) { B = -C.y; }

        float div = 0.5 * (R - L + T - B);
        gl_FragColor = vec4(div, 0.0, 0.0, 1.0);
    }
`
  );

  const curlShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uVelocity;

    void main () {
        float L = texture2D(uVelocity, vL).y;
        float R = texture2D(uVelocity, vR).y;
        float T = texture2D(uVelocity, vT).x;
        float B = texture2D(uVelocity, vB).x;
        float vorticity = R - L - T + B;
        gl_FragColor = vec4(0.5 * vorticity, 0.0, 0.0, 1.0);
    }
`
  );

  const vorticityShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision highp float;
    precision highp sampler2D;

    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uVelocity;
    uniform sampler2D uCurl;
    uniform float curl;
    uniform float dt;

    void main () {
        float L = texture2D(uCurl, vL).x;
        float R = texture2D(uCurl, vR).x;
        float T = texture2D(uCurl, vT).x;
        float B = texture2D(uCurl, vB).x;
        float C = texture2D(uCurl, vUv).x;

        vec2 force = 0.5 * vec2(abs(T) - abs(B), abs(R) - abs(L));
        force /= length(force) + 0.0001;
        force *= curl * C;
        force.y *= -1.0;

        vec2 velocity = texture2D(uVelocity, vUv).xy;
        velocity += force * dt;
        velocity = min(max(velocity, -1000.0), 1000.0);
        gl_FragColor = vec4(velocity, 0.0, 1.0);
    }
`
  );

  const pressureShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uPressure;
    uniform sampler2D uDivergence;

    void main () {
        float L = texture2D(uPressure, vL).x;
        float R = texture2D(uPressure, vR).x;
        float T = texture2D(uPressure, vT).x;
        float B = texture2D(uPressure, vB).x;
        float C = texture2D(uPressure, vUv).x;
        float divergence = texture2D(uDivergence, vUv).x;
        float pressure = (L + R + B + T - divergence) * 0.25;
        gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);
    }
`
  );

  const gradientSubtractShader = compileShader(
    gl.FRAGMENT_SHADER,
    `
    precision mediump float;
    precision mediump sampler2D;

    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uPressure;
    uniform sampler2D uVelocity;

    void main () {
        float L = texture2D(uPressure, vL).x;
        float R = texture2D(uPressure, vR).x;
        float T = texture2D(uPressure, vT).x;
        float B = texture2D(uPressure, vB).x;
        vec2 velocity = texture2D(uVelocity, vUv).xy;
        velocity.xy -= vec2(R - L, T - B);
        gl_FragColor = vec4(velocity, 0.0, 1.0);
    }
`
  );

  const blit = (() => {
    gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(
      gl.ARRAY_BUFFER,
      new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]),
      gl.STATIC_DRAW
    );
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(
      gl.ELEMENT_ARRAY_BUFFER,
      new Uint16Array([0, 1, 2, 0, 2, 3]),
      gl.STATIC_DRAW
    );
    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
    gl.enableVertexAttribArray(0);

    return (target, clear = false) => {
      if (target == null) {
        gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
      } else {
        gl.viewport(0, 0, target.width, target.height);
        gl.bindFramebuffer(gl.FRAMEBUFFER, target.fbo);
      }
      if (clear) {
        gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.clear(gl.COLOR_BUFFER_BIT);
      }
      gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
    };
  })();

  function CHECK_FRAMEBUFFER_STATUS() {
    let status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
    if (status != gl.FRAMEBUFFER_COMPLETE)
      console.trace('Framebuffer error: ' + status);
  }

  let dye;
  let velocity;
  let divergence;
  let curl;
  let pressure;
  let bloom;
  let bloomFramebuffers = [];
  let sunrays;
  let sunraysTemp;

  let ditheringTexture = createTextureAsync('LDR_LLL1_0.png');

  const blurProgram = new Program(blurVertexShader, blurShader);
  const copyProgram = new Program(baseVertexShader, copyShader);
  const clearProgram = new Program(baseVertexShader, clearShader);
  const colorProgram = new Program(baseVertexShader, colorShader);
  const checkerboardProgram = new Program(baseVertexShader, checkerboardShader);
  const bloomPrefilterProgram = new Program(
    baseVertexShader,
    bloomPrefilterShader
  );
  const bloomBlurProgram = new Program(baseVertexShader, bloomBlurShader);
  const bloomFinalProgram = new Program(baseVertexShader, bloomFinalShader);
  const sunraysMaskProgram = new Program(baseVertexShader, sunraysMaskShader);
  const sunraysProgram = new Program(baseVertexShader, sunraysShader);
  const splatProgram = new Program(baseVertexShader, splatShader);
  const advectionProgram = new Program(baseVertexShader, advectionShader);
  const divergenceProgram = new Program(baseVertexShader, divergenceShader);
  const curlProgram = new Program(baseVertexShader, curlShader);
  const vorticityProgram = new Program(baseVertexShader, vorticityShader);
  const pressureProgram = new Program(baseVertexShader, pressureShader);
  const gradienSubtractProgram = new Program(
    baseVertexShader,
    gradientSubtractShader
  );

  const displayMaterial = new Material(baseVertexShader, displayShaderSource);

  function initFramebuffers() {
    let simRes = getResolution(config.SIM_RESOLUTION);
    let dyeRes = getResolution(config.DYE_RESOLUTION);

    const texType = ext.halfFloatTexType;
    const rgba = ext.formatRGBA;
    const rg = ext.formatRG;
    const r = ext.formatR;
    const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;

    gl.disable(gl.BLEND);

    if (dye == null)
      dye = createDoubleFBO(
        dyeRes.width,
        dyeRes.height,
        rgba.internalFormat,
        rgba.format,
        texType,
        filtering
      );
    else
      dye = resizeDoubleFBO(
        dye,
        dyeRes.width,
        dyeRes.height,
        rgba.internalFormat,
        rgba.format,
        texType,
        filtering
      );

    if (velocity == null)
      velocity = createDoubleFBO(
        simRes.width,
        simRes.height,
        rg.internalFormat,
        rg.format,
        texType,
        filtering
      );
    else
      velocity = resizeDoubleFBO(
        velocity,
        simRes.width,
        simRes.height,
        rg.internalFormat,
        rg.format,
        texType,
        filtering
      );

    divergence = createFBO(
      simRes.width,
      simRes.height,
      r.internalFormat,
      r.format,
      texType,
      gl.NEAREST
    );
    curl = createFBO(
      simRes.width,
      simRes.height,
      r.internalFormat,
      r.format,
      texType,
      gl.NEAREST
    );
    pressure = createDoubleFBO(
      simRes.width,
      simRes.height,
      r.internalFormat,
      r.format,
      texType,
      gl.NEAREST
    );

    initBloomFramebuffers();
    initSunraysFramebuffers();
  }

  function initBloomFramebuffers() {
    let res = getResolution(config.BLOOM_RESOLUTION);

    const texType = ext.halfFloatTexType;
    const rgba = ext.formatRGBA;
    const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;

    bloom = createFBO(
      res.width,
      res.height,
      rgba.internalFormat,
      rgba.format,
      texType,
      filtering
    );

    bloomFramebuffers.length = 0;
    for (let i = 0; i < config.BLOOM_ITERATIONS; i++) {
      let width = res.width >> (i + 1);
      let height = res.height >> (i + 1);

      if (width < 2 || height < 2) break;

      let fbo = createFBO(
        width,
        height,
        rgba.internalFormat,
        rgba.format,
        texType,
        filtering
      );
      bloomFramebuffers.push(fbo);
    }
  }

  function initSunraysFramebuffers() {
    let res = getResolution(config.SUNRAYS_RESOLUTION);

    const texType = ext.halfFloatTexType;
    const r = ext.formatR;
    const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;

    sunrays = createFBO(
      res.width,
      res.height,
      r.internalFormat,
      r.format,
      texType,
      filtering
    );
    sunraysTemp = createFBO(
      res.width,
      res.height,
      r.internalFormat,
      r.format,
      texType,
      filtering
    );
  }

  function createFBO(w, h, internalFormat, format, type, param) {
    gl.activeTexture(gl.TEXTURE0);
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(
      gl.TEXTURE_2D,
      0,
      internalFormat,
      w,
      h,
      0,
      format,
      type,
      null
    );

    let fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(
      gl.FRAMEBUFFER,
      gl.COLOR_ATTACHMENT0,
      gl.TEXTURE_2D,
      texture,
      0
    );
    gl.viewport(0, 0, w, h);
    gl.clear(gl.COLOR_BUFFER_BIT);

    let texelSizeX = 1.0 / w;
    let texelSizeY = 1.0 / h;

    return {
      texture,
      fbo,
      width: w,
      height: h,
      texelSizeX,
      texelSizeY,
      attach(id) {
        gl.activeTexture(gl.TEXTURE0 + id);
        gl.bindTexture(gl.TEXTURE_2D, texture);
        return id;
      },
    };
  }

  function createDoubleFBO(w, h, internalFormat, format, type, param) {
    let fbo1 = createFBO(w, h, internalFormat, format, type, param);
    let fbo2 = createFBO(w, h, internalFormat, format, type, param);

    return {
      width: w,
      height: h,
      texelSizeX: fbo1.texelSizeX,
      texelSizeY: fbo1.texelSizeY,
      get read() {
        return fbo1;
      },
      set read(value) {
        fbo1 = value;
      },
      get write() {
        return fbo2;
      },
      set write(value) {
        fbo2 = value;
      },
      swap() {
        let temp = fbo1;
        fbo1 = fbo2;
        fbo2 = temp;
      },
    };
  }

  function resizeFBO(target, w, h, internalFormat, format, type, param) {
    let newFBO = createFBO(w, h, internalFormat, format, type, param);
    copyProgram.bind();
    gl.uniform1i(copyProgram.uniforms.uTexture, target.attach(0));
    blit(newFBO);
    return newFBO;
  }

  function resizeDoubleFBO(target, w, h, internalFormat, format, type, param) {
    if (target.width == w && target.height == h) return target;
    target.read = resizeFBO(
      target.read,
      w,
      h,
      internalFormat,
      format,
      type,
      param
    );
    target.write = createFBO(w, h, internalFormat, format, type, param);
    target.width = w;
    target.height = h;
    target.texelSizeX = 1.0 / w;
    target.texelSizeY = 1.0 / h;
    return target;
  }

  function createTextureAsync(url) {
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT);
    gl.texImage2D(
      gl.TEXTURE_2D,
      0,
      gl.RGB,
      1,
      1,
      0,
      gl.RGB,
      gl.UNSIGNED_BYTE,
      new Uint8Array([255, 255, 255])
    );

    let obj = {
      texture,
      width: 1,
      height: 1,
      attach(id) {
        gl.activeTexture(gl.TEXTURE0 + id);
        gl.bindTexture(gl.TEXTURE_2D, texture);
        return id;
      },
    };

    let image = new Image();
    image.onload = () => {
      obj.width = image.width;
      obj.height = image.height;
      gl.bindTexture(gl.TEXTURE_2D, texture);
      gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, image);
    };
    image.src = url;

    return obj;
  }

  function updateKeywords() {
    let displayKeywords = [];
    if (config.SHADING) displayKeywords.push('SHADING');
    if (config.BLOOM) displayKeywords.push('BLOOM');
    if (config.SUNRAYS) displayKeywords.push('SUNRAYS');
    displayMaterial.setKeywords(displayKeywords);
  }

  let lastUpdateTime = Date.now();
  let colorUpdateTimer = 0.0;

  function update() {
    const dt = calcDeltaTime();
    if (resizeCanvas()) initFramebuffers();
    updateColors(dt);
    applyInputs();
    if (!config.PAUSED) step(dt);
    render(null);
    requestAnimationFrame(update);
  }

  function calcDeltaTime() {
    let now = Date.now();
    let dt = (now - lastUpdateTime) / 1000;
    dt = Math.min(dt, 0.016666);
    lastUpdateTime = now;
    return dt;
  }

  function resizeCanvas() {
    let width = scaleByPixelRatio(canvas.clientWidth);
    let height = scaleByPixelRatio(canvas.clientHeight);
    if (canvas.width != width || canvas.height != height) {
      canvas.width = width;
      canvas.height = height;
      return true;
    }
    return false;
  }

  function updateColors(dt) {
    if (!config.COLORFUL) return;

    colorUpdateTimer += dt * config.COLOR_UPDATE_SPEED;
    if (colorUpdateTimer >= 1) {
      colorUpdateTimer = wrap(colorUpdateTimer, 0, 1);
      pointers.forEach((p) => {
        p.color = generateColor();
      });
    }
  }

  function applyInputs() {
    if (splatStack.length > 0) multipleSplats(splatStack.pop());

    pointers.forEach((p) => {
      if (p.moved) {
        p.moved = false;
        splatPointer(p);
      }
    });
  }

  function step(dt) {
    gl.disable(gl.BLEND);

    curlProgram.bind();
    gl.uniform2f(
      curlProgram.uniforms.texelSize,
      velocity.texelSizeX,
      velocity.texelSizeY
    );
    gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.read.attach(0));
    blit(curl);

    vorticityProgram.bind();
    gl.uniform2f(
      vorticityProgram.uniforms.texelSize,
      velocity.texelSizeX,
      velocity.texelSizeY
    );
    gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.read.attach(0));
    gl.uniform1i(vorticityProgram.uniforms.uCurl, curl.attach(1));
    gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
    gl.uniform1f(vorticityProgram.uniforms.dt, dt);
    blit(velocity.write);
    velocity.swap();

    divergenceProgram.bind();
    gl.uniform2f(
      divergenceProgram.uniforms.texelSize,
      velocity.texelSizeX,
      velocity.texelSizeY
    );
    gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.read.attach(0));
    blit(divergence);

    clearProgram.bind();
    gl.uniform1i(clearProgram.uniforms.uTexture, pressure.read.attach(0));
    gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE);
    blit(pressure.write);
    pressure.swap();

    pressureProgram.bind();
    gl.uniform2f(
      pressureProgram.uniforms.texelSize,
      velocity.texelSizeX,
      velocity.texelSizeY
    );
    gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence.attach(0));
    for (let i = 0; i < config.PRESSURE_ITERATIONS; i++) {
      gl.uniform1i(pressureProgram.uniforms.uPressure, pressure.read.attach(1));
      blit(pressure.write);
      pressure.swap();
    }

    gradienSubtractProgram.bind();
    gl.uniform2f(
      gradienSubtractProgram.uniforms.texelSize,
      velocity.texelSizeX,
      velocity.texelSizeY
    );
    gl.uniform1i(
      gradienSubtractProgram.uniforms.uPressure,
      pressure.read.attach(0)
    );
    gl.uniform1i(
      gradienSubtractProgram.uniforms.uVelocity,
      velocity.read.attach(1)
    );
    blit(velocity.write);
    velocity.swap();

    advectionProgram.bind();
    gl.uniform2f(
      advectionProgram.uniforms.texelSize,
      velocity.texelSizeX,
      velocity.texelSizeY
    );
    if (!ext.supportLinearFiltering)
      gl.uniform2f(
        advectionProgram.uniforms.dyeTexelSize,
        velocity.texelSizeX,
        velocity.texelSizeY
      );
    let velocityId = velocity.read.attach(0);
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocityId);
    gl.uniform1i(advectionProgram.uniforms.uSource, velocityId);
    gl.uniform1f(advectionProgram.uniforms.dt, dt);
    gl.uniform1f(
      advectionProgram.uniforms.dissipation,
      config.VELOCITY_DISSIPATION
    );
    blit(velocity.write);
    velocity.swap();

    if (!ext.supportLinearFiltering)
      gl.uniform2f(
        advectionProgram.uniforms.dyeTexelSize,
        dye.texelSizeX,
        dye.texelSizeY
      );
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read.attach(0));
    gl.uniform1i(advectionProgram.uniforms.uSource, dye.read.attach(1));
    gl.uniform1f(
      advectionProgram.uniforms.dissipation,
      config.DENSITY_DISSIPATION
    );
    blit(dye.write);
    dye.swap();
  }

  function render(target) {
    if (config.BLOOM) applyBloom(dye.read, bloom);
    if (config.SUNRAYS) {
      applySunrays(dye.read, dye.write, sunrays);
      blur(sunrays, sunraysTemp, 1);
    }

    if (target == null || !config.TRANSPARENT) {
      gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
      gl.enable(gl.BLEND);
    } else {
      gl.disable(gl.BLEND);
    }

    if (!config.TRANSPARENT)
      drawColor(target, normalizeColor(config.BACK_COLOR));
    if (target == null && config.TRANSPARENT) drawCheckerboard(target);
    drawDisplay(target);
  }

  function drawColor(target, color) {
    colorProgram.bind();
    gl.uniform4f(colorProgram.uniforms.color, color.r, color.g, color.b, 1);
    blit(target);
  }

  function drawCheckerboard(target) {
    checkerboardProgram.bind();
    gl.uniform1f(
      checkerboardProgram.uniforms.aspectRatio,
      canvas.width / canvas.height
    );
    blit(target);
  }

  function drawDisplay(target) {
    let width = target == null ? gl.drawingBufferWidth : target.width;
    let height = target == null ? gl.drawingBufferHeight : target.height;

    displayMaterial.bind();
    if (config.SHADING)
      gl.uniform2f(
        displayMaterial.uniforms.texelSize,
        1.0 / width,
        1.0 / height
      );
    gl.uniform1i(displayMaterial.uniforms.uTexture, dye.read.attach(0));
    if (config.BLOOM) {
      gl.uniform1i(displayMaterial.uniforms.uBloom, bloom.attach(1));
      gl.uniform1i(
        displayMaterial.uniforms.uDithering,
        ditheringTexture.attach(2)
      );
      let scale = getTextureScale(ditheringTexture, width, height);
      gl.uniform2f(displayMaterial.uniforms.ditherScale, scale.x, scale.y);
    }
    if (config.SUNRAYS)
      gl.uniform1i(displayMaterial.uniforms.uSunrays, sunrays.attach(3));
    blit(target);
  }

  function applyBloom(source, destination) {
    if (bloomFramebuffers.length < 2) return;

    let last = destination;

    gl.disable(gl.BLEND);
    bloomPrefilterProgram.bind();
    let knee = config.BLOOM_THRESHOLD * config.BLOOM_SOFT_KNEE + 0.0001;
    let curve0 = config.BLOOM_THRESHOLD - knee;
    let curve1 = knee * 2;
    let curve2 = 0.25 / knee;
    gl.uniform3f(bloomPrefilterProgram.uniforms.curve, curve0, curve1, curve2);
    gl.uniform1f(
      bloomPrefilterProgram.uniforms.threshold,
      config.BLOOM_THRESHOLD
    );
    gl.uniform1i(bloomPrefilterProgram.uniforms.uTexture, source.attach(0));
    blit(last);

    bloomBlurProgram.bind();
    for (let i = 0; i < bloomFramebuffers.length; i++) {
      let dest = bloomFramebuffers[i];
      gl.uniform2f(
        bloomBlurProgram.uniforms.texelSize,
        last.texelSizeX,
        last.texelSizeY
      );
      gl.uniform1i(bloomBlurProgram.uniforms.uTexture, last.attach(0));
      blit(dest);
      last = dest;
    }

    gl.blendFunc(gl.ONE, gl.ONE);
    gl.enable(gl.BLEND);

    for (let i = bloomFramebuffers.length - 2; i >= 0; i--) {
      let baseTex = bloomFramebuffers[i];
      gl.uniform2f(
        bloomBlurProgram.uniforms.texelSize,
        last.texelSizeX,
        last.texelSizeY
      );
      gl.uniform1i(bloomBlurProgram.uniforms.uTexture, last.attach(0));
      gl.viewport(0, 0, baseTex.width, baseTex.height);
      blit(baseTex);
      last = baseTex;
    }

    gl.disable(gl.BLEND);
    bloomFinalProgram.bind();
    gl.uniform2f(
      bloomFinalProgram.uniforms.texelSize,
      last.texelSizeX,
      last.texelSizeY
    );
    gl.uniform1i(bloomFinalProgram.uniforms.uTexture, last.attach(0));
    gl.uniform1f(bloomFinalProgram.uniforms.intensity, config.BLOOM_INTENSITY);
    blit(destination);
  }

  function applySunrays(source, mask, destination) {
    gl.disable(gl.BLEND);
    sunraysMaskProgram.bind();
    gl.uniform1i(sunraysMaskProgram.uniforms.uTexture, source.attach(0));
    blit(mask);

    sunraysProgram.bind();
    gl.uniform1f(sunraysProgram.uniforms.weight, config.SUNRAYS_WEIGHT);
    gl.uniform1i(sunraysProgram.uniforms.uTexture, mask.attach(0));
    blit(destination);
  }

  function blur(target, temp, iterations) {
    blurProgram.bind();
    for (let i = 0; i < iterations; i++) {
      gl.uniform2f(blurProgram.uniforms.texelSize, target.texelSizeX, 0.0);
      gl.uniform1i(blurProgram.uniforms.uTexture, target.attach(0));
      blit(temp);

      gl.uniform2f(blurProgram.uniforms.texelSize, 0.0, target.texelSizeY);
      gl.uniform1i(blurProgram.uniforms.uTexture, temp.attach(0));
      blit(target);
    }
  }

  function splatPointer(pointer) {
    let dx = pointer.deltaX * config.SPLAT_FORCE;
    let dy = pointer.deltaY * config.SPLAT_FORCE;
    splat(pointer.texcoordX, pointer.texcoordY, dx, dy, pointer.color);
  }

  function multipleSplats(amount) {
    for (let i = 0; i < amount; i++) {
      const color = generateColor();
      color.r *= 10.0;
      color.g *= 10.0;
      color.b *= 10.0;
      const x = Math.random();
      const y = Math.random();
      const dx = 1000 * (Math.random() - 0.5);
      const dy = 1000 * (Math.random() - 0.5);
      splat(x, y, dx, dy, color);
    }
  }

  function splat(x, y, dx, dy, color) {
    splatProgram.bind();
    gl.uniform1i(splatProgram.uniforms.uTarget, velocity.read.attach(0));
    gl.uniform1f(
      splatProgram.uniforms.aspectRatio,
      canvas.width / canvas.height
    );
    gl.uniform2f(splatProgram.uniforms.point, x, y);
    gl.uniform3f(splatProgram.uniforms.color, dx, dy, 0.0);
    gl.uniform1f(
      splatProgram.uniforms.radius,
      correctRadius(config.SPLAT_RADIUS / 100.0)
    );
    blit(velocity.write);
    velocity.swap();

    gl.uniform1i(splatProgram.uniforms.uTarget, dye.read.attach(0));
    gl.uniform3f(splatProgram.uniforms.color, color.r, color.g, color.b);
    blit(dye.write);
    dye.swap();
  }

  function correctRadius(radius) {
    let aspectRatio = canvas.width / canvas.height;
    if (aspectRatio > 1) radius *= aspectRatio;
    return radius;
  }

  eventListeners.mouseDown = (e) => {
    if (config.PAUSED) return;
    if (config.TRIGGER !== 'click') return;
    let posX = scaleByPixelRatio(e.clientX);
    let posY = scaleByPixelRatio(e.clientY);
    let pointer = pointers.find((p) => p.id == -1);
    if (pointer == null) pointer = new pointerPrototype();
    updatePointerDownData(pointer, -1, posX, posY);
  };
  document.addEventListener('mousedown', eventListeners.mouseDown);

  eventListeners.mouseMove = (e) => {
    if (config.PAUSED) return;
    let pointer = pointers[0];
    let posX = scaleByPixelRatio(e.clientX);
    let posY = scaleByPixelRatio(e.clientY);
    if (config.TRIGGER === 'click') {
      if (!pointer.down) return;
    } else if (config.TRIGGER === 'hover') {
      if (!pointer.down) {
        pointer.down = true;
        pointer.texcoordX = posX / canvas.width;
        pointer.texcoordY = 1.0 - posY / canvas.height;
        pointer.prevTexcoordX = pointer.texcoordX; // 初始化 prev 位置
        pointer.prevTexcoordY = pointer.texcoordY;
        pointer.color = generateColor(); // 生成新颜色
      }
    }
    updatePointerMoveData(pointer, posX, posY);
  };
  document.addEventListener('mousemove', eventListeners.mouseMove);

  eventListeners.mouseUp = (e) => {
    if (config.PAUSED) return;
    if (config.TRIGGER !== 'click') return;
    updatePointerUpData(pointers[0]);
  };
  window.addEventListener('mouseup', eventListeners.mouseUp);

  eventListeners.touchStart = (e) => {
    e.preventDefault();
    const touches = e.targetTouches;
    while (touches.length >= pointers.length)
      pointers.push(new pointerPrototype());
    for (let i = 0; i < touches.length; i++) {
      let posX = scaleByPixelRatio(touches[i].pageX);
      let posY = scaleByPixelRatio(touches[i].pageY);
      updatePointerDownData(pointers[i + 1], touches[i].identifier, posX, posY);
    }
  };
  document.addEventListener('touchstart', eventListeners.touchStart);

  eventListeners.touchMove = (e) => {
    e.preventDefault();
    const touches = e.targetTouches;
    for (let i = 0; i < touches.length; i++) {
      let pointer = pointers[i + 1];
      if (!pointer.down) continue;
      let posX = scaleByPixelRatio(touches[i].pageX);
      let posY = scaleByPixelRatio(touches[i].pageY);
      updatePointerMoveData(pointer, posX, posY);
    }
  };
  document.addEventListener('touchmove', eventListeners.touchMove);

  eventListeners.touchEnd = (e) => {
    const touches = e.changedTouches;
    for (let i = 0; i < touches.length; i++) {
      let pointer = pointers.find((p) => p.id == touches[i].identifier);
      if (pointer == null) continue;
      updatePointerUpData(pointer);
    }
  };
  window.addEventListener('touchend', eventListeners.touchEnd);

  eventListeners.keyDown = (e) => {
    if (e.code === 'KeyP') config.PAUSED = !config.PAUSED;
    if (e.key === ' ') splatStack.push(parseInt(Math.random() * 20) + 5);
  };
  window.addEventListener('keydown', eventListeners.keyDown);

  function updatePointerDownData(pointer, id, posX, posY) {
    pointer.id = id;
    pointer.down = true;
    pointer.moved = false;
    pointer.texcoordX = posX / canvas.width;
    pointer.texcoordY = 1.0 - posY / canvas.height;
    pointer.prevTexcoordX = pointer.texcoordX;
    pointer.prevTexcoordY = pointer.texcoordY;
    pointer.deltaX = 0;
    pointer.deltaY = 0;
    pointer.color = generateColor();
  }

  function updatePointerMoveData(pointer, posX, posY) {
    pointer.prevTexcoordX = pointer.texcoordX;
    pointer.prevTexcoordY = pointer.texcoordY;
    pointer.texcoordX = posX / canvas.width;
    pointer.texcoordY = 1.0 - posY / canvas.height;
    pointer.deltaX = correctDeltaX(pointer.texcoordX - pointer.prevTexcoordX);
    pointer.deltaY = correctDeltaY(pointer.texcoordY - pointer.prevTexcoordY);
    pointer.moved =
      Math.abs(pointer.deltaX) > 0 || Math.abs(pointer.deltaY) > 0;
  }

  function updatePointerUpData(pointer) {
    pointer.down = false;
  }

  function correctDeltaX(delta) {
    let aspectRatio = canvas.width / canvas.height;
    if (aspectRatio < 1) delta *= aspectRatio;
    return delta;
  }

  function correctDeltaY(delta) {
    let aspectRatio = canvas.width / canvas.height;
    if (aspectRatio > 1) delta /= aspectRatio;
    return delta;
  }

  function generateColor() {
    let c = HSVtoRGB(Math.random(), 1.0, 1.0);
    c.r *= 0.15;
    c.g *= 0.15;
    c.b *= 0.15;
    return c;
  }

  function HSVtoRGB(h, s, v) {
    let r, g, b, i, f, p, q, t;
    i = Math.floor(h * 6);
    f = h * 6 - i;
    p = v * (1 - s);
    q = v * (1 - f * s);
    t = v * (1 - (1 - f) * s);

    switch (i % 6) {
      case 0:
        (r = v), (g = t), (b = p);
        break;
      case 1:
        (r = q), (g = v), (b = p);
        break;
      case 2:
        (r = p), (g = v), (b = t);
        break;
      case 3:
        (r = p), (g = q), (b = v);
        break;
      case 4:
        (r = t), (g = p), (b = v);
        break;
      case 5:
        (r = v), (g = p), (b = q);
        break;
    }

    return {
      r,
      g,
      b,
    };
  }

  function normalizeColor(input) {
    let output = {
      r: input.r / 255,
      g: input.g / 255,
      b: input.b / 255,
    };
    return output;
  }

  function wrap(value, min, max) {
    let range = max - min;
    if (range == 0) return min;
    return ((value - min) % range) + min;
  }

  function getResolution(resolution) {
    let aspectRatio = gl.drawingBufferWidth / gl.drawingBufferHeight;
    if (aspectRatio < 1) aspectRatio = 1.0 / aspectRatio;

    let min = Math.round(resolution);
    let max = Math.round(resolution * aspectRatio);

    if (gl.drawingBufferWidth > gl.drawingBufferHeight)
      return { width: max, height: min };
    else return { width: min, height: max };
  }

  function getTextureScale(texture, width, height) {
    return {
      x: width / texture.width,
      y: height / texture.height,
    };
  }

  function scaleByPixelRatio(input) {
    let pixelRatio = window.devicePixelRatio || 1;
    return Math.floor(input * pixelRatio);
  }

  function hashCode(s) {
    if (s.length == 0) return 0;
    let hash = 0;
    for (let i = 0; i < s.length; i++) {
      hash = (hash << 5) - hash + s.charCodeAt(i);
      hash |= 0; // Convert to 32bit integer
    }
    return hash;
  }

  function destroy() {
    // 停止动画循环
    if (animationFrameId) {
      cancelAnimationFrame(animationFrameId);
    }

    // 移除事件监听器
    document.removeEventListener('mousedown', eventListeners.mouseDown);
    document.removeEventListener('mousemove', eventListeners.mouseMove);
    window.removeEventListener('mouseup', eventListeners.mouseUp);
    document.removeEventListener('touchstart', eventListeners.touchStart);
    document.removeEventListener('touchmove', eventListeners.touchMove);
    window.removeEventListener('touchend', eventListeners.touchEnd);
    window.removeEventListener('keydown', eventListeners.keyDown);

    // 释放WebGL资源
    if (gl) {
      // 销毁程序
      [
        blurProgram,
        copyProgram,
        clearProgram,
        colorProgram,
        checkerboardProgram,
        bloomPrefilterProgram,
        bloomBlurProgram,
        bloomFinalProgram,
        sunraysMaskProgram,
        sunraysProgram,
        splatProgram,
        advectionProgram,
        divergenceProgram,
        curlProgram,
        vorticityProgram,
        pressureProgram,
        gradienSubtractProgram,
      ].forEach((program) => {
        if (program && program.program) gl.deleteProgram(program.program);
      });

      // 销毁纹理和FBO
      const destroyFBO = (fbo) => {
        if (fbo && fbo.texture) gl.deleteTexture(fbo.texture);
        if (fbo && fbo.fbo) gl.deleteFramebuffer(fbo.fbo);
      };

      [dye, velocity, divergence, curl, pressure, bloom, sunrays, sunraysTemp]
        .filter(Boolean)
        .forEach((fbo) => {
          if (fbo.read) destroyFBO(fbo.read);
          if (fbo.write) destroyFBO(fbo.write);
          if (Array.isArray(fbo)) fbo.forEach(destroyFBO);
        });

      bloomFramebuffers.forEach(destroyFBO);
      if (ditheringTexture && ditheringTexture.texture)
        gl.deleteTexture(ditheringTexture.texture);
    }

    // 清理全局引用
    pointers.length = 0;
    splatStack.length = 0;
    canvas.width = 1;
    canvas.height = 1;
  }

  resizeCanvas();
  updateKeywords();
  initFramebuffers();
  multipleSplats(parseInt(Math.random() * 20) + 5);
  update();

  return {
    destroy,
  };
}
